The proposal by the administration of President Barack Obama to scan license plates of all drivers in selected cities in an effort to locate illegal immigrants is not exactly legal, Judge Andrew Napolitano claimed Wednesday.

"It isn't constitutional," Napolitano, a former New Jersey Superior Court judge, told Fox News' "Happening Now" show. "The Constitution establishes a bar over which the government must go before it can commence any investigation about anybody.

"Law enforcement is not allowed to use its powers for no reason, or on a hunch, or a whim. It has to have a reason that they can articulate as to who did what wrong before they can start investigating," he added.

As a means to track illegal immigrants, Napolitano said the plan "isn't efficient." He explained the government must answer, "Why are you investigating?" because he said, "You can't just investigate anybody you want."

The national license plate tracking system under the Department of Homeland Security would scan plates of drivers in cities across the country, which would then go into a national database, according to Fox News.

A commercial enterprise would take the photographs and store them in a database, but Napolitano said the government would have "complete electronic access to all the information in the servers of the private company."

"This is a proposal, not enacted by the Congress, not voted on by any of the people's representatives, but snuck into a budget by some bureaucrats who decided to go out and spend this money to hire this company to take pictures of every license plate in select major cities in the United States," he said.

A new federal police department within DHS would oversee the program, Napolitano said.

"These are federal cops taking pictures of people as they drive their cars on highways. This has never been done before," he said.

Napolitano said the proposed program would "destroy our freedom," and the erosion of rights would create a world where children "will never know what privacy was."